Inhibitors of gpIIb/IIIa have proven to be efficacious as anti-thrombotic agents for use in treatment of cardiovascular disease. Abciximab, a chimeric human-murine monoclonal antibody, was the first gpIIb/IIIa antagonist developed. (Binkley et al, Nucleic Acid Research 23:3198-3205 (1995)). Eptifibatide, a small peptide, and Tirofiban, a small non-peptide, both interact with and inhibit the function of the beta-3 (β3) sub-unit of gpIIb/IIIa (Scarborough et al, J. Biol. Chem. 268:1066-1073 (1993), Bednar et al, J. Pharmacol. Exp. Ther. 285:1317-1326 (1998), Hartman et al, J. Med. Chem. 35:4640-4642 (1992)). The two main drugs used clinically are Abciximab and Eptifibatide.
Abciximab is approved for use in patients undergoing percutaneous coronary intervention (PCI) and is being studied for use in acute coronary syndromes (ACS). The EPIC trial revealed that Abciximab reduced the morbidity and mortality of cardiovascular disease, but also showed an increase in major bleeding episodes from 7% to 14% and an increase in blood transfusions from 10% to 21% (Lincoff et al, Am. J. Cardiel. 79:286-291 (1997)). Eptifibatide is also used in PCI and, like Abciximab, is an effective antithrombotic with a trend towards increased bleeding (The PURSUIT Trial Investigators, N. Eng. J. Med. 339:436-443 (1998)). In addition to bleeding complications, readministration is a potential concern, especially with Abciximab, where initial administration was associated with a human antichimeric antibody response in 7% of patients (Tcheng, Am. Heart J. 139:S38-45 (2000)). Finally, thrombocytopenia is also seen in patients who receive gpIIb/IIIa antagonists. Severe thrombocytopenia (<20,000/μl) occurs in almost 0.5% of patients after intravenous administration (Topal et al, Lancet 353:227-231 (1999)). The most pressing issue with these drugs, given the clinical environment in which they are used, is the need to turn off or reverse their activity quickly. This would allow physicians to reduce the side effects of the medications should they become a risk to the health and safety of the patient and would also allow surgeons to perform immediate coronary bypass graft surgery, should the need arise. Thus, the development of new gpIIb/IIIa inhibitors with matched antidotes is a medical priority.
Ribonucleic acid ligands, or aptamers, are a new class of drug compounds ideally suited to anticoagulation therapy. They bind to their targets with high affinity and specificity, are only slightly immunogenic and their bioavailability can be tailored to suit a particular clinical need (Nimjee et al, Annu. Rev. Med. 56:555-583 (2005)). More recently, research has shown that these drugs can be controlled with antidotes both in vitro and in vivo (Nimjee et al, Molecular Therapy: the Journal of the American Society of Gene Therapy (2006), Mol. Ther. 14:408-45 Epub Jun. 9, 2006, Rusconi et al, Nat. Biotechnol. 22:1423-1428 (2004), Rusconi et al, Nature 419:90-94 (2002)).
The present invention relates to RNA ligands (aptamers) that inhibit receptor function and activity, including platelet function and activity. The invention further relates to specific, rationally-designed antidotes that can reverse this inhibitory effect.